1. Field of the Invention
The present invention generally relates to an optical transceiver, and in particular, to an optical transceiver used in a bidirectional optical communication field.
2. Description of the Related Art
With an increase demand in transmission of high-quality broadcasting, Internet data, and video conferences at individual homes, the establishment of Fiber to the Home (FTTH) networks using optical fibers is being actively carried out.
An economical optical communication solution, i.e., a 1.25 Gbps Ethernet Passive Optical Network (EPON), includes a single central office (an Optical Line Terminal: OLT) that provides a communication service and a plurality of subscribers including Optical Network Terminals (ONTs) for communication with the central office. In operation, the central office splits an optical signal using a splitter for transmission to the subscribers.
A communication charge imposed on each subscriber includes the cost associated with the maintenance and equipment fees of an ONT and the central office. Thus, it is desirable to minimize the costs of the ONT and the OLT to minimize the communication charge imposed on each subscriber.
U.S. Pat. No. 4,767,171 filed on Feb. 11, 1987 by Siemens Corp. and U.S. Pat. No. 6,075,635 filed on Sep. 4, 1997 by Lucent Technologies Inc. disclose bidirectional optical transceiving modules.
Briefly, the bidirectional optical transceiving module of Siemens Corp. includes three lenses, making its structure complicated and increasing its cost. On the other hand, the bidirectional optical transceiving module of Lucent Technologies Inc. includes two lenses, but the optical axes of an optical fiber and a filter are not easy to arrange and an expensive aspherical lens is additionally required to minimize the occurrence of aberration.
Moreover, the bidirectional optical transceiving module of Lucent Technologies, Inc. has an asymmetric structure in which the incident plane of the optical fiber is arranged remotely from the optical axis to improve the optical coupling efficiency between an optical signal generated from a light source and the optical fiber, causing a tracking error according to a change in temperature or degradation in reliability.